The invention relates to an apparatus for tempering tools, for use on the form or mold tools of extrusion forming machines. In such injection molding tools, conduction circuits for a coolant are provided as well as ducts for the inflow and discharge of the coolant. Valves are also provided which control the throughflow or volumetric flow rate of the coolant.
The extrusion forming machines currently known comprise tool cooling or tempering systems in which the throughflow of the coolant, generally water, can be adjusted by turning handwheels, for example. Using an inspection glass or tube, the injection molding operator is able to estimate the quantity of medium flowing through the injection molding tool in a given time span. Obviously, with this procedure, the assessment of the quantity of coolant is imprecise. Heretofore, the actual temperature of the tool has been determined in an equally imprecise manner. Thus, for example, the tool temperature is deduced from the quality of the injection molded product or the tool temperature is determined from the outside, e.g. by applying a temperature measuring instrument to the halves of the tool, or by simply touching them with the hand.
This known system has serious disadvantages. Not only is such a system inaccurate the optimum volumetric rate of flow of coolant is difficult to determine and adjust. Other disadvantages are the fact that, during operation of the extrusion forming machine, various disturbances occur, e.g. changes in the pressure or temperature of the coolant, variations in the ambient temperature, changes in the diameter of the tempering channel or the transfer of heat. Moreover, any production stoppages will change the temperature of the tool, which known extrusion forming machines will not react to directly.